1008-988/988 = 0.0202
Is that what you want ? That's the % difference between those two numbers.
If you want the midpoint:
1008+988 / 2 = 998
If you want the 3rd quartile:
988 + (1008-988 * 0.75) = 1003
I have no idea if that's what you want, but here si what i think is what you...